From August 1977 through October 1984, 241 patients underwent aortic valve replacement with the Ionescu-Shiley prosthesis. The average age was 50.8 years (range 15 to 78). Aortic valve replacement was performed alone in 121 patients (50.2%) and with associated surgery in 120 (49.8%). Cumulative duration of follow-up was 1,260.08 patient-years, with a mean follow-up of 5.32 years per patient. Five patients were lost to follow-up. There were 26 hospital deaths and 15 late deaths (1.19% per patient-year). The expected 10.5 year actuarial survival rate was 82 +/- 2.9%. Twelve thromboembolic episodes occurred in 7 patients (7 central and 5 peripheral). The linearized thromboembolic rate was 0.95% per patient-year: 0.32% for patients with isolated aortic valve replacement and 0.63% for patients with concomitant surgery. Freedom from thromboembolic events at 10.5 years was 78 +/- 12%. Structural valve failure was found in 24 patients (1.9% per patient-year) with an actuarial rate of freedom for primary tissue failure of 72.6 +/- 6.1% at 10.5 years. Reoperation was required in 39 cases (3.09% per patient-year) due to primary tissue failure (n:24), paravalvular leak (n:7), infective endocarditis (n:6) and valve thrombosis (n:2). In conclusion, this pericardial bioprosthesis has demonstrated an adequate performance at mid and long-term follow-up, but somehow less satisfactory than previously reported.